"Flow Cytometric immunophenotyping is a sensitive technique for analysis of benign and malignant tumors. We are studying the refinement of this technique and its application to diagnosis and measurement of prognostic markers in different systems. We are studying the flow cytometric immunophenotype of CLL and correlating the expression of specific antigens with morphology, cytogenetics and clinical course. Data from this study may provide prognostic markers for this disease. We have continued our studies of myelodysplastic syndrome (MDS) and have defined diagnostic indicators of abnormal maturation in myeloid, megakaryocytic and erythroid lineages. We have shown that flow cytometric immunophenotyping is more sensitive than morphology in MDS. We are currently correlating cytogenetic abnormalities with immunophenotype in this disease. This information is being used to improve our ability to diagnose early myelodysplasia and differentiate it from other conditions with cytopenias. We have refined methods for flow cytometric monitoring of patient specimens for apoptosis induced by chemotherapy and have been able to detect apoptosis in specific cell populations. This has allowed us to demonstrate different sensitivities of specific cell lineages to chemotherapeutic agents. We have initiated a study of clonal cytotoxic T-cell populations that arise in patients with B-cell neoplasia to determine prognostic importance as well as resulting difficulties in minimal residual disease detection. The laboratory has an ongoing interest in detection of minimal and residual lymphoma. We are using multiparametric approaches to improve the sensitivity of detection of monoclonal B-cell populations. By targeting abnormal patterns of antigen expression (eg CD10, CD5, CD23, FMC7, or abnormal intensity of antigen expression) by neoplastic B-cells in light chain detection, we are attempting to detect very small numbers of neoplastic B-cells among admixed polyclonal B-cells."